Anti-skinning agents having a mixture of organic compounds and coating compositions containing them

ABSTRACT

The invention relates to anti-skinning agents containing mixtures of organic compounds (combinations of additives), whereby the organic compounds are selected from the groups of organic hydroxylamines, and β-dicarbonyl compounds and/or selected derivatives of formic acid and also relates to compositions containing them, especially oxidatively drying paints or coating compositions.

FIELD OF THE INVENTION

The invention relates to anti-skinning agents containing mixtures oforganic compounds (combinations of additives) and coating compositionscontaining them. The organic compounds are selected from the groups oforganic hydroxylamines, and β-dicarbonyl compounds and/or selectedderivatives of formic acid. The invention further relates tocompositions containing these anti-skinning agents, like coatingcompositions such as oxidatively drying paints.

BACKGROUND OF THE INVENTION

Colorless and pigmented oxidatively drying paints and coatings based onoxidatively drying oils, alkyd resins, epoxy esters and otheroxidatively drying refined oils are known. These oils and binderscrosslink oxidatively under the influence of oxygen (preferablyatmospheric oxygen) by means of the addition of driers, such as metalcarboxylates of transition metals. If this crosslinking takes placebefore the product is actually used, they can form a solid binder film,a skin, on the surface when stored in open or closed containers. This ishighly undesirable and should therefore be avoided since it makes thepaint more difficult to work with, and commonly interferes with theuniform distribution of the driers. The accumulation of the driers inthe paint skin that forms can lead to considerable delays in the dryingof the paint when it is applied.

Skinning in the paint film after application is also disadvantageous.Excessively rapid drying of the surface of the paint prevents the lowerfilm layers from drying evenly because they are shielded from oxygen,which is prevented from sufficiently penetrating into and dispersingwithin the paint film. This can lead among other things to flow problemsin the paint film, adhesion problems, or insufficiently hard films.

It is known to add organic substances to the paint that inhibit thereaction of the drier metal with (atmospheric) oxygen by binding theoxygen or by complexing of the drier metal. Formulations of knowncompounds that are suitable for this purpose can be found e.g. in H.Kittel “Lehrbuch der Lacke und Beschichtungen”, Colomb Verlag 1976; J.Bieleman “Lackadditive” Wiley VCH 1998 or Römpp Lexikon “Lacke undDruckfarben”, Thieme Verlag 1998.

Furthermore, DE-A 3 418 988 describes the use of aliphatic α-hydroxyketones as anti-skinning agents, and DE-A 1 519 103 disclosesN,N-dialkylated hydroxylamines for this purpose. Because of their lowvolatility, however, these agents can lead to severe delays in dryingand often also to reduced film hardness values, so that their possibleapplications are limited. They have not been able to gain acceptance asanti-skinning agents.

EP-A 0 903 380 describes the use of α-keto-functionalised carboxylicacids and dicarboxylic acids and of derivatives thereof, optionally incombination with diketo compounds, as anti-skinning agents. Adisadvantageous property of such products lies in their limitedstability and hence restricted storage life.

Finally, pyrazole or imidazole derivatives, optionally in combinationwith aliphatic diketones, in particular acetylacetone, are recommendedfor this purpose in WO 00/11090. However, the cited aromatic amines cancause severe discoloration in the coating composition and also in theapplied paint film and likewise give rise to severe delays in drying.

Oximes (in particular butanone oxime) or suitable phenolic compounds aremostly used today as anti-skinning agents in industry. The phenolicanti-skinning agents display a significant delay in surface drying,however, such that alone they are only suitable for certain coatingcompositions. Oximes such as e.g. methyl ethyl ketoxime orbutyraldoxime, on the other hand, display only slight delays in surfacedrying due to their volatility. The most significant disadvantage of theoximes, which are widely used today, lies in their toxicity. Inlong-term inhalation studies on rats and mice, for example, an increasedoccurrence of liver tumors was observed after exposure to butanoneoxime, as a result of which the German MAK committee has classified thesubstance as a category III A 2 carcinogen (MAK list 1997) [MAK=maximumallowable concentration in the workplace]. As a consequence of this,users have to observe elaborate personal protection precautions whenworking with paints containing oximes as anti-skinning agents.

It is an object of the present invention to develop organic compoundswhich prevent skinning in paints and coating compositions over anextended period and display only a slight delay in surface drying.Furthermore, the film hardness values obtained in the resulting films orcoatings should not be negatively influenced and no discoloration shouldbe caused. The products should display no disadvantageous toxicologicalproperties.

It is another object of the invention that the organic compounds can beincorporated into many different oxidatively drying paints and coatingsand by virtue of their physical properties can be usedstraight-forwardly and for many purposes in corresponding coatingcompositions.

Surprisingly it was found that these requirements could be achieved bythe use of mixtures containing the organic compounds described below. Inparticular, the above-mentioned disadvantages of the specifiedhydroxylamines as anti-skinning agents could also be avoided bycombining such substances with the additional compounds described below,and hence products that better satisfy requirements as anti-skinningagents are obtained.

In air-drying paints the mixtures according to the invention aresuitable for preventing undesirable skinning, for improving the completedrying of paint films after application and for reducing the tendency ofthe applied paint film to discolor.

SUMMARY OF THE INVENTION

The invention relates to an anti-skinning agent containing

a) an organic compound of formula (I)

where

R¹ and R² mutually independently represent hydrogen, a linear orbranched, saturated or unsaturated C₁-C₂₀ aliphatic radical, which canoptionally be mono- or polysubstituted, or a C₆-C₁₂ aryl radical, aC₇-C₁₄ araliphatic radical or a C₅-C₇ cycloaliphatic radical,

and either or both of

b) an organic compound of formula (II)

where

R³ represents hydrogen, a hydroxyl radical, a substituted orunsubstituted, saturated or unsaturated C₁-C₁₉ aliphatic radical, aC₁-C₇ alkoxy radical, or an amine radical —NR⁷R⁸,

R⁴ represents hydrogen, hydroxyl radical, a substituted orunsubstituted, saturated or unsaturated C₁-C₁₉ aliphatic radical, aC₁-C₇ alkoxy radical, or an amine radical —NR⁹R¹⁰,

R⁷ and R⁸ mutually independently represent hydrogen or a C₁-C₆ aliphaticradical,

R⁹ and R¹⁰ mutually independently hydrogen or a C₁-C₆ aliphatic radical,and

c) an organic compound of formula (III)

where

R⁵ represents hydrogen, a hydroxyl radical or a C₁-C₇ alkoxy radical and

R⁶ represents hydrogen or an amine radical —NR¹¹R¹²,

R¹¹ and R¹² mutually independently represent hydrogen, substituted orunsubstituted C₁-C₆ aliphatic radical, or substituted or unsubstitutedC₅-C₇ cycloaliphatic radical, or amine radical —NR¹R²

with the proviso that R⁵ and R⁶ are not simultaneously hydrogen.

The invention also relates to compositions of matter containing theseanti-skinning agents.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the invention mixtures of organic compounds offormulae (I) to (III) are used alone or as solutions or dispersions oremulsions in water and/or organic solvents. Suitable organic solventsinclude all conventional solvents, such as aromatics, white spirits,ketones, alcohols, ethers and fatty acid esters.

For the use according to the invention the organic compounds of formulae(I) to (III) can be used in a broad range of mixtures with one another.They are preferably used in the ratio (I):(II) or (III)=0.1:10 to 10:0.1parts. In a mixture consisting of all three components, each of thecomponents can mutually independently preferably be used in the ratio0.1 to 10 to each of the other components used. They can be used in pureform or in aqueous solution or aqueous dispersion or emulsion or in theform of solutions in organic solvents, whereby aqueous in this contextis intended to mean that water is either the sole solvent or is added ina quantity of over 50 wt. % relative to the solvent blend together withconventional organic solvents (e.g. alcohols).

The amount of anti-skinning agents primarily depends on the content ofbinder and drier used in the particular coating composition. As ageneral rule between 0.001 and 2.0 wt. % of mixtures of compoundsaccording to formulae (I) to (III) should be added. Preferred amounts tobe used are 0.01 to 0.5 wt. %, relative in each case to the overallrecipe of the coating composition. The amounts can also depend on thetype of binder and the pigments used. Thus in special systems therelative amount of additive to be used can also be greater than 2.0 wt.% (relative to the overall recipe).

It is an advantage of the anti-skinning agent of the present inventionthat it reliably prevent skinning in a wide range of binders and whenused with various driers but does not unfavorably influence other dryingproperties of the paint.

The invention is further illustrated but is not intended to be limitedby the following examples in which all parts and percentages are byweight unless otherwise specified.

EXAMPLES

The following embodiments of the mixtures of organic compounds offormulae (I) to (III) that are suitable for use according to theinvention as anti-skinning agents are cited by way of example:

a) 19% diethyl hydroxylamine, 22% diethyl formamide, 59% water;

b) 19% diethyl hydroxylamine, 22% diethyl formamide, 59% ethanol;

c) 15% diethyl hydroxylamine, 9% 2,4-pentane dione, 60% ethanol, 16%water;

d) 19% diethyl hydroxylamine, 17.5% N-methyl acetoacetamide, 63.5%ethanol;

e) 10% diethyl hydroxylamine, 9% hydrazine ethyl carboxylate, 79.5%ethanol, 1.5% water;

f) 25% dibenzyl hydroxylamine, 15% N-methyl acetoacetamide, 10% ethanol,50% acetone;

g) 23% dibenzyl hydroxylamine, 10% diethyl formamide, 10% ethanol, 57%acetone;

h) 10% diethyl hydroxylamine, 9% malonic acid, 10% diethyl formamide,60% ethanol, 11% water;

i) 10% diethyl hydroxylamine, 9% ethyl formiate, 50% ethanol, 31% water;

j) 10% diethyl hydroxylamine, 10% ethyl acetoacetate, 78% water;

k) 10% diethyl hydroxylamine, 9% dimethyl malonate, 60% ethanol, 21%water;

l) 10% diethyl hydroxylamine, 9% malonic acid, 50% ethanol, 31% water;

m) 20% hydroxylamine, 15% N-methyl acetoacetamide, 30% ethanol, 35%water;

n) 24% hydroxylamine, 11% hydrazine ethyl carboxylate, 25% ethanol, 40%water.

Examples of the Use of Anti-Skinning Agents According to the Invention

1. 0.15 g of a cobalt-containing drier (trade name Octa-Soligen Cobalt 6from Borchers GmbH, contains 6 wt. % Co), 0.33 g of azirconium-containing drier (trade name Octa-Soligen Zirkon 18 fromBorchers GmbH, contains 18 wt. % Zr) and 0.18 g of a calcium-containingdrier (trade name Octa-Soligen Calcium 4 from Borchers GmbH, contains 4wt. % calcium) were added to a coating composition consisting of 25.0 gof a long-oil, high-gloss white alkyd resin topcoat (binder solidscontent 68 wt. %). 0.018 g of the mixture listed under a) was added tothe formulation and the time taken for a skin to form on the surface ofa closed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for 33 days in this case. By way of comparison, theskinning time for a sample without anti-skinning additive determinedunder identical conditions was 5 days, that for a sample containing aconventional, suitable amount of butanone oxime (0.12 g) was 18 days.The color coordinate b* of a corresponding paint film with a 100 μm wetfilm thickness (according to CIELAB, corresponding to DIN 6174)determined after a storage period of 1 week resulted in a value when themixture according to the invention was used that was 0.7463 points lowerthan the tristimulus value of the sample containing butanone oxime,determined under identical conditions, as a result of which a reducedyellowing of the film was indicated.

2. 0.38 g of a cobalt-containing mixed drier (trade name Octa-SoligenTrockner 203 from Borchers GmbH, contains 1.2 wt. % Co, 3.2 wt. % zincand 7.2 wt. % barium) was added to a coating composition consisting of25.0 g of a high-gloss white alkyd resin topcoat (binder solids content36.9 wt. %). 0.046 g of the mixture listed under c) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for more than 27 days in this case. By way of comparison,the skinning time for a sample without anti-skinning additive determinedunder identical conditions was 2 days and that for a sample containing aconventional, suitable amount of butanone oxime (0.041 g) was 10 days.The gloss of the paint film (according to DIN 67530) determined after astorage period of 1 week was determined as 85.9 points (measured at 20°)and 92.8 points (measured at 60°) when the mixture according to theinvention was used. By way of comparison, the gloss of the paint filmfrom the sample without anti-skinning additive determined underidentical conditions was 81.6 points (measured at 20°) and 88.5 points(measured at 60°), that of the film from the sample containing butanoneoxime was 82.1 and 89.9 points (at 20° and 60° respectively). The colorco-ordinate b* of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174) determinedafter a storage period of 1 week resulted in a value when the mixtureaccording to the invention was used that was 0.300 points lower than thetristimulus value of the sample containing butanone oxime, determinedunder identical conditions, as a result of which a reduced yellowing ofthe film was indicated.

3. 0.10 g of a cobalt-containing drier (trade name Octa-Soligen Cobalt 6from Borchers GmbH, contains 6 wt. % Co) and 0.4 g of acalcium-containing drier (trade name Octa-Soligen Calcium 4 fromBorchers GmbH, contains 4 wt. % calcium) were added to a coatingcomposition consisting of 30.0 g of a long-oil alkyd resin (trade nameAlkydal U 601 from Bayer AG) and 2.2 g white spirit D 60. 0.005 g of themixture listed under d) was added to the formulation and the time takenfor a skin to form on the surface of a closed 125 ml PE beaker filled toapprox. ¼ was established. Skinning was prevented for more than 50 daysin this case. By way of comparison, the skinning time for a samplewithout anti-skinning additive determined under identical conditions was6 days, the skinning time for a sample containing a conventional,suitable amount (0.05 g) of butanone oxime was 16 days and that for asample containing an identical amount (0.001 g) of diethyl hydroxylaminein the same solvent was 7 days. The König pendulum hardness (determinedaccording to DIN 53 157, 100 μm wet film thickness) of a paint film towhich the mixture according to the invention had been added was 97seconds after a storage period of 1 week. By way of comparison, thependulum hardness of the paint film from the sample withoutanti-skinning additive determined under identical conditions was 96seconds, that of the film from the sample containing butanone oxime waslikewise 97 seconds and that of the film from the sample containingdiethyl hydroxylamine was 93 seconds, in each case after a storageperiod of 1 week.

4. 0.40 g of a cobalt-containing mixed drier (trade name Octa-SoligenTrockner 203 from Borchers GmbH, contains 1.2 wt. % Co, 3.2 wt. % zincand 7.2 wt. % barium) was added to a coating composition consisting of30.0 g of a high-gloss white alkyd resin topcoat (binder solids content36.9 wt. %). 0.005 g of the mixture listed under b) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for 42 days in this case. By way of comparison, theskinning time for a sample without anti-skinning agent determined underidentical conditions was 8 days, the skinning time for a samplecontaining a conventional, suitable amount (0.05 g) of butanone oximewas 21 days and that for a sample containing an identical amount (0.001g) of diethyl hydroxylamine in the same solvent was likewise 21 days.The drying time of a corresponding paint film (100 μm wet filmthickness) from the mixture according to the invention was 12 h (scratchdrying according to test specification 100-94 from Borchers GmbH). Thedrying time of a sample without anti-skinning additive determined underidentical conditions was 10 h 30 min., that of the sample containingbutanone oxime was determined as 10 h. The drying time of the paint filmfrom the sample containing diethyl hydroxylamine was 14 h. The colorco-ordinate b* of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174) determinedafter a storage period of 1 week was 2.2754 when the mixture accordingto the invention was used. The tristimulus values for the sampleswithout anti-skinning agent and with an identical amount (0.001 g) ofdiethyl hydroxylamine in the same solvent determined under identicalconditions were 2.4214 and 2.4434 units respectively, as a result ofwhich a reduced yellowing of the coating composition containing themixture according to the invention was indicated.

5. 0.10 g of a cobalt-containing drier (trade name Octa-Soligen Cobalt 6from Borchers GmbH, contains 6 wt. % Co) and 0.4 g of acalcium-containing drier (trade name Octa-Soligen Calcium 4 fromBorchers GmbH, contains 4 wt. % calcium) were added to a coatingcomposition consisting of 30.0 g of a long-oil alkyd resin (trade nameAlkydal U 601 from Bayer AG) and 2.2 g white spirit D 60. 0.023 g of themixture listed under h) was added to the formulation and the time takenfor a skin to form on the surface of a closed 125 ml PE beaker filled toapprox. ¼ was established. Skinning was prevented for 22 days in thiscase. By way of comparison, the skinning time for a sample withoutanti-skinning additive determined under identical conditions was 3 daysand that for a sample containing a conventional, suitable amount ofbutanone oxime (0.05 g) was 10 days. The König pendulum hardness(determined according to DIN 53 157, 100 μm wet film thickness) of apaint film to which the mixture according to the invention had beenadded was 75 seconds after a storage period of 1 week. By way ofcomparison, the pendulum hardness of the paint film from the samplewithout anti-skinning additive determined under identical conditions was73 seconds, that of the film from the sample containing butanone oximewas 76 seconds.

6. 0.18 g of a cobalt-containing drier (trade name Trockner 69 fromBorchers GmbH, contains 6 wt. % Co and 9 wt. % zirconium) and 0.4 g of acalcium-containing drier (trade name Octa-Soligen Calcium 10 fromBorchers GmbH, contains 10 wt. % calcium) were added to a coatingcomposition consisting of 40.0 g of a long-oil alkyd resin (trade nameAlkydal F 681 from Bayer AG), 4.0 g white spirit D 60, 4.0 g xylene, 1.0g n-butanol. 0.04 g of the mixture listed under e) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for 102 days in this case. By way of comparison, theskinning time for a sample without anti-skinning additive determinedunder identical conditions was 11 days, the skinning time for a samplecontaining a conventional, suitable amount (0.10 g) of butanone oximewas 26 days and that for a sample containing an identical amount (0.004g) of diethyl hydroxylamine in the same solvent blend was likewise 26days. The König pendulum hardness (determined according to DIN 53157,100 μm wet film thickness) of a paint film to which the mixtureaccording to the invention had been added was 41 seconds after a storageperiod of 1 week. By way of comparison, the pendulum hardness of thepaint film from the sample without anti-skinning additive determinedunder identical conditions was 29 seconds, that of the film from thesample containing butanone oxime was 32 seconds and that of the filmfrom the sample containing diethyl hydroxylamine was 37 seconds, in eachcase after a storage period of 1 week.

7. 0.38 g of a cobalt-containing mixed drier (trade name Octa-SoligenTrockner 203 from Borchers GmbH, contains 1.2 wt. % Co, 3.2 wt. % zincand 7.2 wt. % barium) was added to a coating composition consisting of25.0 g of a high-gloss white alkyd resin topcoat (binder solids content36.9 wt. %). 0.069 g of the mixture listed under i) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for more than 21 days in this case. By way of comparison,the skinning time for a sample without anti-skinning additive determinedunder identical conditions was 2 days and that for a sample containing aconventional, suitable amount of butanone oxime (0.041 g) was 10 days.The color coordinate b* of a corresponding paint film with a 100 μm wetfilm thickness (according to CIELAB, corresponding to DIN 6174)determined after a storage period of 1 week resulted in a value when themixture according to the invention was used that was 0.166 points lowerthan the tristimulus value of the sample containing butanone oxime,determined under identical conditions. At the same time a tristimulusvalue was obtained that was 0.3117 points lower than the tristimulusvalue of the sample without anti-skinning agent determined underidentical conditions, as a result of which a reduced yellowing of thefilm was indicated. The gloss of the paint film (according to DIN 67530)determined after a storage period of 1 week was determined as 87.8points (measured at 20°) and 95.6 points (measured at 60°) when themixture according to the invention was used. By way of comparison, thegloss of the paint film from the sample without anti-skinning additivedetermined under identical conditions was 81.6 points (measured at 20°)and 88.5 points (measured at 60°), that of the film from the samplecontaining butanone oxime was 82.1 and 89.9 points (at 20° and 60°respectively).

8. 0.20 g of a cobalt-containing drier (trade name Octa-Soligen Cobalt 6from Borchers GmbH, contains 6 wt. % Co), 0.25 g of azirconium-containing drier (trade name Octa-Soligen Zirkon 18 fromBorchers GmbH, contains 18 wt. % Zr) and 0.46 g of a calcium-containingdrier (trade name Octa-Soligen Calcium 10 from Borchers GmbH, contains10 wt. % calcium) were added to a coating composition consisting of 40.0g of a high-gloss white alkyd resin topcoat (binder solids content 38wt. %). 0.092 g of the mixture listed under k) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for more than 28 days in this case. By way of comparison,the skinning time for a sample without anti-skinning additive determinedunder identical conditions was 5 days and that for a sample containing aconventional, suitable amount of butanone oxime (0.162 g) was 21 days.The König pendulum hardness (determined according to DIN 53157, 100 μmwet film thickness) of a paint film to which the mixture according tothe invention had been added was 79 seconds after a storage period of 1week. By way of comparison, the pendulum hardness of the paint film fromthe sample without anti-skinning additive and that of the film from thesample containing butanone oxime, determined under identical conditions,was in each case 76 seconds after a storage period of 1 week. The colorco-ordinate b* of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174) determinedafter a storage period of 1 week resulted in a value when the mixtureaccording to the invention was used that was 0.293 points lower than thetristimulus value of the sample containing butanone oxime, determinedunder identical conditions, as a result of which a reduced yellowing ofthe film is indicated when the mixture according to the invention isused.

9. 0.20 g of a cobalt-containing drier (trade name Octa-Soligen Cobalt 6from Borchers GmbH, contains 6 wt. % Co), 0.25 g of azirconium-containing drier (trade name Octa-Soligen Zirkon 18 fromBorchers GmbH, contains 18 wt. % Zr) and 0.46 g of a calcium-containingdrier (trade name Octa-Soligen Calcium 10 from Borchers GmbH, contains10 wt. % calcium) were added to a coating composition consisting of 40.0g of a high-gloss white alkyd resin topcoat (binder solids content 38wt. %). 0.092 g of the mixture listed under I) was added to theformulation and the time taken for a skin to form on the surface of aclosed 125 ml PE beaker filled to approx. ¼ was established. Skinningwas prevented for more than 28 days in this case. By way of comparison,the skinning time for a sample without anti-skinning additive determinedunder identical conditions was 5 days and that for a sample containing aconventional, suitable amount of butanone oxime (0.162 g) was 21 days.The König pendulum hardness (determined according to DIN 53157, 100 μmwet film thickness) of a paint film to which the mixture according tothe invention had been added was 78 seconds after a storage period of 1week. By way of comparison, the pendulum hardness of the paint film fromthe sample without anti-skinning additive and that of the film from thesample containing butanone oxime, determined under identical conditions,was in each case 76 seconds after a storage period of 1 week. The filmbrightness L of a corresponding paint film with a 100 μm wet filmthickness (according to CIELAB, corresponding to DIN 6174), determinedafter a storage period of 1 week, resulted in a value when the mixtureaccording to the invention was used that was 0.318 points higher thanthe value for the sample containing butanone oxime, determined underidentical conditions, as a result of which a higher film brightness inthe coating containing the mixture according to the invention wasindicated.

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is:
 1. An anti-skinning agent comprising a) an organiccompound of formula (I)

 where R¹ and R² mutually independently represent hydrogen, a linear orbranched, saturated or unsaturated C₁-C₂₀ aliphatic radical, which canoptionally be mono- or polysubstituted, or a C₆-C₁₂ aryl radical, aC₇-C₁₄ araliphatic radical or a C₅-C₇ cycloaliphatic radical, b) anorganic compound of formula (II)

 where R³ represents hydrogen, a hydroxyl radical, a saturated orunsaturated C₁-C₁₉ aliphatic radical, a C₁-C₇ alkoxy radical, or anamine radical —NR⁷R⁸, R⁴ represents hydrogen, hydroxyl radical, asaturated or unsaturated C₁-C₁₉ aliphatic radical, a C₁-C₇ alkoxyradical, or an amine radical —NR⁹R¹⁰, R⁷ and R⁸ mutually independentlyrepresent hydrogen or a C₁-C₆ aliphatic radical, R⁹ and R¹⁰ mutuallyindependently hydrogen or a C₁-C₆ aliphatic radical, and c) an organiccompound of formula (III)

 where R⁵ represents hydrogen, a hydroxyl radical or a C₁-C₇ alkoxyradical and R⁶ represents hydrogen or an amine radical —NR¹¹R¹², R¹¹ andR¹² mutually independently represent hydrogen, C₁-C₆ aliphatic radical,or C₅-C₇ cycloaliphatic radical, or amine radical —NR¹R² with theproviso that R⁵ and R⁶ are not simultaneously hydrogen.
 2. Theanti-skinning agent of claim 1 further comprising water and/or anorganic solvent.
 3. The anti-skinning agent of claim 1 wherein R³represents a substituted C₁-C₁₉ aliphatic radical, a substituted C₁-C₇alkoxy radical, or a substituted amine radical —NR⁷R⁸, and R⁴represents, a substituted C₁-C₁₉ aliphatic radical, a substituted C₁-C₇alkoxy radical, or a substituted amine radical —NR⁹R¹⁰, R¹¹ and R¹²mutually independently represent a substituted C₁-C₆ aliphatic radical,or a substituted C₅-C₇ cycloaliphatic radical, or a substituted amineradical —NR¹R².
 4. The anti-skinning agent of claim 1 wherein thecompounds of formula (I) to (III) are in the form of aqueous dispersionsor emulsions.
 5. A composition of matter comprising the anti-skinningagent of claim
 1. 6. The composition of matter of claim 5 wherein theamount of anti-skinning agent is between 0.001 and 2.0 wt. % based onthe composition.
 7. The composition of matter of claim 5 wherein theamount of anti-skinning agent is between 0.01 to 0.5 wt. %, based on thecomposition.
 8. The composition of matter of claim 5 further comprisinga pigment.
 9. The composition of matter of claim 5 wherein thecomposition is a colorless or pigmented paint, a coating, a printing inkbased on oxidatively drying binders, an oxidatively drying paint system,or a spraying agent in a printing ink.